An image forming apparatus equipped with a detachable toner cartridge has been proposed, in which an image forming operation is prohibited when the toner in the toner cartridge is consumed. Hereinafter, this condition is referred to as “toner empty” or “toner empty condition”.
The toner empty is memorized in a memory of the apparatus. To recover from the toner empty condition, a user opens a front door of the apparatus to exchange the toner cartridge and then closes the front door. This allows a toner supply device in the apparatus starts supplying the toner from the new toner cartridge into the associated developing device. This technique is disclosed in JP 11-237785 A, for example. When the toner supply operation is properly performed and thereby a required amount of toner is accommodated in the developing device, the image forming operation can be restarted.
There may be case in which the toner empty is detected and then a power saving condition is started or a power supply is turned off while leaving the empty cartridge in the apparatus. In this instance, the toner supply operation is supposed to be done after a recovery operation is completed, i.e., the power saving condition is cleared or the power supply is turned on. Meanwhile, if the toner cartridge exchange has been completed before the recovery operation, the toner supply is properly performed. Otherwise, no toner is supplied from the toner cartridge to the developing device after the subsequent recovery operation. Also, if this condition is detected repeatedly, it can erroneously be determined that the toner supply device is inoperative, which prohibits the start of the image forming operation and/or increases waiting time before the initiation of the image forming operation.